The present invention relates to a hydrokinetic coupling apparatus, especially for a motor vehicle, of the type described and shown for example in the document WO-A-94/07058.
That document describes and shows an apparatus of the type comprising a generally transversely oriented wall adapted to be coupled in rotation to a driving shaft and carrying a so-called guide sleeve fixed centrally to it, a piston mounted for sealed sliding movement along a cylindrical surface of the sleeve and defining, with the sleeve and the transverse wall, a variable volume chamber which is bounded radially on the outside by an annular ring, together with friction liners which are adapted to be gripped axially, respectively, between the piston and the annular ring and between the annular ring and the internal face of the transverse wall.
In one known embodiment which is described and shown in the document FR-A-2 702 262, it is known to provide an annular disc for driving the piston in rotation by means of the sleeve, the disc being coupled in rotation and axially to the latter and being connected to the piston by means of elastically deformable tongues, the disc extending radially inwards in facing relationship with a transversely oriented annular surface portion of the sleeve against which it is in axial engagement.
In accordance with the embodiment described and shown in the said document, the central sleeve is fixed to the driving disc, or coupling disc, firstly by means of a set of complementary teeth or splines which are formed, respectively, in the circular inner edge of the driving disc and in an axial end portion of the said cylindrical surface of the sleeve, and secondly, by an end seaming operation which immobilises the splined driving disc axially in axial abutment against the annular surface portion of the sleeve.
A disadvantage of this solution is that it calls for relatively complex forming and/or machining operations on the driving disc and the central sleeve, and it requires a seaming operation, which is difficult to perform without involving accidental deformations of the components, and which makes it necessary to use for the central sleeve a steel such that it can be machined and deformed so that it can be seamed.
In order to overcome these drawbacks, the document FR-A-2 749 632 proposed a solution in which the design of the sleeve is much simplified, and in which the coupling disc includes a central portion which extends radially inwards and is welded to the sleeve, the coupling disc with its central portion being interposed axially between the piston and the turbine wheel. That design simplifies the means for coupling and fastening together the coupling disc and sleeve, but it provides no solution as to centring and fastening of the sleeve, in particular with respect to the transverse wall of the cover plate, while fastening and centring of the sleeve in this case make it necessary to form a central hole in the wall and then to carry out a welding operation.
The design of the transverse wall of the cover plate is therefore complicated, as are the sealing arrangements of the apparatus generally.
The document FR-A-2 766 894 proposed a further design, in which the coupling disc is disposed between the piston and the transverse wall of the cover plate, and it has a central portion which extends radially inwards and which is interposed axially between a facing portion of the sleeve and a facing portion of the inner face of the cover plate.
In the design described in that document, and in its various embodiments, the central portion of the coupling disc is fixed either to the transverse wall or to the sleeve, and the latter is fixed and centred with respect to the cover plate in the same way as in the document FR-A-2 749 632, that is to say by means of a hole in a central sleeve which is formed for this purpose in the transverse wall of the cover plate, and by means of a welding operation.
The document FR-A-2 634 849 further proposes another design in which the coupling disc is disposed axially between the piston and the transverse wall of the cover plate, and here again it is coupled in rotation and coupled axially with the sleeve by splined coupling means and by an operation of welding or seaming.
As in the document mentioned earlier, the sleeve is centred and fixed axially through a central hole in the transverse wall of the cover plate.
The invention aims to propose a new design for an apparatus of the type set forth above, including a coupling disc the design of which is simple, and which, in particular, enables a cover plate to be used having a transverse wall with no central hole for fastening and centring of the sleeve.
To this end, the invention proposes hydrokinetic coupling apparatus, especially for a motor vehicle, of the type including a generally transversely oriented wall adapted to be coupled in rotation to a driving shaft, a central sleeve, and a piston mounted for sealed sliding movement along a cylindrical surface of the central sleeve and defining, with the sleeve and the transverse wall, a variable volume control chamber which is bounded radially on the outside by at least one annular ring which is adapted to be gripped between the piston and the internal rear face of the transverse wall, and of the type comprising an annular disc for coupling the piston in rotation with the sleeve, which is disposed axially between the piston and the transverse wall, and which includes a central portion extending radially inwards in facing relationship with an annular internal surface portion of the transverse wall, against which it is in axial engagement and to which it is directly or indirectly fixed, characterised in that the sleeve is attached axially to the said central portion of the annular coupling disc, with respect to which the sleeve is radially centred.
According to further features of the invention:
the central portion of the coupling disc is interposed axially between an annular transverse front end surface of the sleeve and the said annular rear inner surface portion of the transverse wall.
the central portion of the coupling disc is fixed to the said annular front transverse end surface of the sleeve by welding or adhesive bonding.
the central portion of the coupling disc is fixed to the said annular transverse front end surface of the sleeve by seaming.
the central portion of the coupling disc is fixed to the said annular front transverse end surface of the sleeve in elastic mating engagement in the axial direction.
the sleeve includes a convex cylindrical surface for centring the central portion of the coupling disc.
the central portion of the coupling disc extends radially inwards beyond the sleeve, in particular to constitute a calibrated orifice for supplying oil to the control chamber.
the central portion of the coupling disc is made in one piece with the sleeve.
the central portion of the coupling disc is extended by at least one axially oriented annular first portion which extends towards the rear, and of which the convex cylindrical peripheral surface constitutes the said cylindrical surface for sliding movement of the piston.
the said axially oriented annular first portion is extended radially inwards by a radially oriented annular portion, and then by an axially oriented second annular portion which extends forward towards the inner face of the transverse wall.
the free front terminal edge of the said axially oriented annular portion is in axial engagement against the said annular rear internal surface portion of the transverse wall.
the free front terminal edge of the said axially oriented annular second portion is welded to the said annular rear internal surface portion of the transverse wall.
the central portion of the coupling disc is extended radially inwards by an axially oriented annular portion extending towards the rear, and in that an annular element constituting a hub is interposed radially between the convex cylindrical peripheral surface of the axially oriented annular portion and the piston which is mounted for sliding movement on the convex cylindrical peripheral surface of the said annular element.
the central portion of the coupling disc is fixed to the said annular rear internal surface portion of the transverse wall by welding or adhesive bonding.
fluid feed passages for the generally radially oriented variable volume control chamber are formed at the interface between the central portion of the coupling disc and the said annular rear internal surface portion of the transverse wall, and/or at the interface between the sleeve and the central portion of the coupling disc.
the said passages are formed in bosses, slots and/or holes formed in the transverse wall and/or in the central portion of the coupling disc and/or in the sleeve.
the annular coupling disc is connected to the piston by means of elastically deformable tongues.
the elastically deformable tongues are made in one piece with the coupling disc.